Propeller blade fairing



Jan. 26, 1943. E. MARTIN PROPELLER BLADE FAIRINGS Filed Aug. 3l, 1940 ATTO RNEY Patented Jan. 26, 1943 PROPELLER BLADE FAIRING Erle Martin, West Hartford, Conn., assignor to United Aircraft Corp Conn., a corporation o oration, East Hartford, fDelaware Application August 3l, 1940, Serial No. 355,073

9 Claims. (Cl. 17o-159) This invention relates to improvements in propeller blades and has particular reference to an improved shank fairing cuil" for a blade of the type normally having a rounded shank portion.

An object of the invention resides in the provision of an improved light weight fairing structure which may be readily attached to the blade and detached therefrom.

A further object resides in the provision of improved means for retaining alight weight fairing cuff of the character indicated on the shank portion of a propeller blade.

A still further object resides in the provision of an improved propeller blade shank fairing cuit of the character indicated which may conveniently be formed of two separable hollow members adapted to be secured together in operative position upon the blade and held in proper position on the blade by suitable means provided at each end of the shank fairing cuil.

Other objects and advantages will be more particularly pointed out hereinafter or will become apparent as the description proceeds.

In the accompanying drawing, in which like reference numerals are used to designate similar parts throughout, there is illustrated a suitable mechanical embodiment for the purpose of disclosing the invention. The drawing, however, is for the purpose of illustration only and is not to be taken as limiting or restricting the invention since it will be apparent to those skilled in the art that various changes in the illustrated embodiment may be restorted to without in any way exceeding the scope of the invention.

In the drawing;

Fig. 1 is a side-elevational view partly in section of a fragmentary portion of a propeller blade shank fairing cui constructed according to the invention in operative position upon the blade:C

Fig. 2 is a transverse sectional view on the line 2-2 of Fig. 1.

Fig. 3 is a transverse sectional view on the line 3-3 of Fig. 1.

Fig. 4 is a transverse sectional view on the line 4-4 of Fig. 1.

Fig. 5 is a longitudinal sectional view of a fragmentary portion of the blade at the outer end of the shank fairing cuff taken on the4 line 5-5 of Fig. 1, and

Fig. 6 is a sectional View of the end of the fairing and end supporting ring shown in Fig. 5 the parts being shown separated to illustrate the4 manner of applying the fairing to the blade.

Referring to the drawing in detail, the numeral I0 generally indicates a propeller blade having a shank portion I2 terminating in a circular end ilange I4 upon which is disposed an anti-friction thrust bearing I6 for retaining the blade end in a suitable hub structure for pitch changing rotational movements about its longitudinal axis. If desired the hub included end portion of the blade may be provided with a suitable wear resisting coating I8 of thermoplastic material. The ange I4 is circular in form and is joined to the adjacent lend of the shank I2 by suitable fillets 20, this end of the shank being circular in cross section and gradually fairing into the airfoil shape of the blade, as is particularly illustrated in Fig. 1. With this construction the inner portion of the blade has a rounded non-streamlined form which, while providing adequate strength, does not have any advantageous reaction on the air surrounding the hub portion of the propeller. It has been found that the efficiency of the propeller can be materially increased and, in those cases where the propeller driving engine has cooling surfaces disposed in the Wake of the propeller, the cooling of the engine can be materially improved by providing the inner or shank portions of the propeller blades with airfoil fairing members or cuis. Since the blade shank provides adequate strength, as mentioned above, it is not desirable to extend the material of the blade itself to provide the fairing structure, particularly where the blades are made of metal, as is usually the case, since this would add unduly to the weight of the blade and the centrifugal forces acting on the blade retaining hub. For these reasons it is advantageous to secure a separate light weight cuil member, as generally indicated at 22, to the shank portion of the blade.

The cuff member is made up of two parts, as indicated at 24 and 26, separable along the leading and trailing edges of the blade as indicated by the lines 28 and 30. These members are somewhat larger than the portion of the blade which they include so that spaces are left between the cuff and the edge portions of the blade, as is clearly indicated in Figs. 2 and 3. Preferably the cuil' contacts the blade along the opposite sides thereof so that the cui will be maintained in proper position on the blade and will not be able to twist relative to the blade under the influence of air and centrifugal forces acting on the cuff. Each cuff member is provided with spaced internal ribs, as indicated at 32, 34 and 36 for reinforcing the relativelythin shell like portions 24 and 26 and providing adequate material for the clamp bolts 38 which secure the two parts of the cu together in operative position upon the blade shank. The

manner that the bushing not only supports the cui! in directions radially of the blade axis but also by means of the abutting surface 4i supports the cuff against slipping longitudinally of the blade under the action of centrifugal force when the propeller is rotating. This member 40 is a relatively xed generallycylindrical member having a length sufcient to provide an adequate bond between the member and the blade surface and is preferably formed of resilient material such as rubber so that it will conform to the interior of the cuff when the two parts of the cuff are clamped together on the blade. 'A rubber ring 42 is also provided at the outer end of the cuil! and is firmly cemented or vulcanized to the blade so that it will materially assist in supporting the cuff on the blade. A'I'his member is given a generally tapered form, as is particularly illustrated in Fig. 5, to provide a continuous bezel for fairing the outer end of the cuff down to the blade surface and is also provided in its inner end with a continuous tongue-like extension 46 provided on the end of each of the cuff members. Adjacent the tongue 46 the cui member is provided with an internal shoulder 48 which bears against the surface of the blade, as particularly illustrated in Fig. 4, to securely position the outer end of the cuff and maintain the extension 46 somewhat spaced`from the blade surface and in line with the groove 44 in the ring member 42. While it has been found convenient to make the ring members 40 and 42 of rubber, it is to be understood that the invention is not limited to this specific material but that other material such as synthetic rubber or thermoplastic materials may be used without in any way exceeding the scope of the invention.

The members 24 and 26 are premolded tc the desired shape and are preferably formed of a suitable thermoplastic material as such a material possesses the advantage of adequate strength with minimum weight. It is apparent, however, that these members could be formed of other materials, such as a light weight metal or alloy. For example, a magnesium or aluminum alloy could be ,used without in any way exceeding the scope of the invention.

In carrying out the invention the ring members 40 and 42 are cemented or vulcanized in place upon the nished blade. These members may be molded in place if desired or may be preformed and slipped on over one end of the blade if their resiliency is sufficient, or may be split and applied to the blade in proper position and then subjected to a bonding process to permanently secure them to the surface of the blade. After the members 40 and 42 are permanently secured in place on the blade the members 24and 26 are applied to the blade in a position somewhat nearer the flanged end of the blade than their operative position. The members are then moved outwardly of the blade until the extension 46 is received in the groove 44 and the clamp nuts 38 are then applied to secure the two parts of the cui together and in their operative position on the blade shank. The members may be easily removed for repair or inspection by simply removing the clamp bolts 38 and slipping the extension 46 out of the groove 44.

While a suitable mechanical embodiment for the purpose of disclosing the invention has been hereinabove described and illustrated in the accompanying drawing, it is to be understood that the invention is not limited to the particular embodiment so illustrated and described, but that such changes in the various parts. their arrangement and the materials of which they are formed, niay be resorted to as come within the scope of the sub-joined claims.

Having now described the invention so that others skilled in the art may clearly understand the same, -what it is desired to secure by Letters Patent is as follows:

1'. A shank fairing for a propeller blade comprising, a pair of hollow thin-walled members which when secured together constitute a body of airfoil contour having an interior space suillcient for the inclusion of the shank portion of the propeller blade therein, and two bands of resilient material surrounding said blade in position to receive the ends of said hollow members and per` manently secured to' said blade to provide end supports for said pair of members when said members are assembled about the shank portion of the blade with their ends compressing said resilient material.

` 2. A shank fairing for a propeller blade comprising, a pair of hollow thin-walled members which when secured together constitute a body of airfoil contour having an interior space suillcient for the inclusion of the shank portion of the propeller blade therein, a cushion of resilient material surrounding and bonded to the propeller blade in position to receive and support the inner end of said body, and a' continuous bezel of resilient material surrounding and bonded to the blade in position to receive and support the outer end of said body.

3. A shank fairing for a propeller blade comprising, a pair of hollow thin-walled members which when secured together constitute a body of airfoil contour having an interior space suillcient for the inclusion of the shank portion of the propeller blade therein, a cushion of resilient material surrounding and bonded to the propeller blade in position to receive and support the inner end of said body, and a continuous bezel of resilient material adapted tc be disposed at the outer end of said body, and a tongue and groove con nection between said bezel and the adjacent end of said body.

4. In combination a shank fairing, a propeller blade having a tip portion at one end and a shank at the other end comprising, a pair of fairing members adapted to be secured together on said shank to thereby form a shank fairing, a band of resilient material permanently secured to said blade shank by being bonded thereto and having a surface facing the shank-end of the propeller blade, said surface providing an abutting surface for said fairing, said fairing surrounding said propeller blade shank on the shank-end side of said resilient band, and having a surface conformed to, coextensive with and abutting said abutting surface of said resilient band to thereby position said fairing on said shank and secure it against movement longitudinally of said blade away from said shank-end.

5. In combination a shank fairing, a propeller blade having a tip portion at one end and a shank at the other end comprising, a pair of fairing members adapted to be secured together on said shank to thereby form a shank fairing, a band of resilient material permanently secured to said thereof, said ring being bonded to said blade adblade adjacent said shank by being bonded thereto and having a surface facing the shank-end of the propeller blade", said surface providing an abutting surface for said fairing. said fairing surrounding said propeller blade shank on the shank-end side of said resilient band, and having a surface conformed to, coextensive with and abutting said abutting surface of said resilient band to thereby position said fairing on said shank and secure ,it against movement longitudinally of said bladefaway from said shank-end.

6. Means for preventing movementpof a shank fairing longitudinally outward of a propeller blade having a shank portion at one end thereof, said means comprising a ring of' resilient material bonded to and encircling said blade shank, the surface of said ring on its side facing the shank end of said blade forming an abutting surface against which the fairing abuts so that the ring forms an abutment for the fairing preventing longitudinal outward movement thereof, said ring being bonded to said blade shank longitudinally outward of said fairing abutting surface.

7. Means for preventing movement of a shank fairing longitudinally outward of a propeller blade. having a shank portion at one end thereof, said means comprising a ring of resilient material bonded to and encircling said blade adjacent said shank, the surface of said ring on its side facing the shank end of said blade forming an abutting surface against which the fairing abuts so that the ring forms an abutment for the fairing preventing longitudinal outward movement jacent said shank longitudinally outward of said fairing abutting surface. l 8. Means for positioning a blade shank fairing and preventing movement thereof longitudinally outward of a propeller blade having a shank portion at one end thereof, said means comprising, spaced rings of resilient material bonded to and encircling the propeller blade adjacent said shank portion, the surface of each ring on the side thereof facing the shank end of said blade forming an abuttingsurface against which the fairing abuts so that each ring forms an abutment for the fairing preventing longitudinal outward movement thereof. said rings forming spaced supports for said fairing.

9. In combination, a propeller blade having a rounded shank portion, resilient material encircling said shank portion adjacent the blade end and secured thereto, and a hollow fairing encircling said shank portion and at least a portion of said resilient material and contacting said resilient material, said resilient material being larger in peripheral dimensions than the smallest corresponding dimension of the fairing adjacenll said material when said fairing is assembled on said material, the surface of said ring facing the shank end of said blade forming an abutting surface against which the fairing abuts so that the ring forms an abutment for the fairing preventing longitudinal outward movement thereof and acts as a support therefor. 

